You can blend and merge shadows and highlights, sharpen dull, blurry images, so they look crisp and clear, add details and tint colors to make a photo stand out, and so, so much more. Pretty much anything you want to do with your photo, you can accomplish with Lightroom. But it is purely a photography tool that's a little outside the regular Adobe design ecosystem. Lightroom is great for photographers who need to manage a large image library and who are prepared to commit to (and pay for) Adobe's cloud storage space.
When you look into photo editing software, one of the first things that'll pop up is Adobe's Lightroom, and for good reason! It's essentially a staple in the photo editing community.